Optical device and imaging apparatus with position sensors and coil motors

ABSTRACT

In a state in which a position sensor for focusing is viewed in the direction of an optical axis, a line connecting the position sensor for focusing to the optical axis is set as a first reference line and a line orthogonal to the first reference line and passing through the optical axis is set as a second reference line. The position sensor for focusing is disposed in a first region of the first region and a second region partitioned by the second reference line. An X-direction VCM and a Y-direction VCM are arranged in the second region. The influence of magnetism from the X-direction VCM and the Y-direction VCM on the position sensor for focusing is suppressed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of PCT International Application No.PCT/JP2017/014509 filed on 7 Apr. 2017, which claims priority under 35U.S.C § 119(a) to Japanese Patent Application No. 2016-090134 filed on28 Apr. 2016. The above application is hereby expressly incorporated byreference, in its entirety, into the present application.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to an optical device and an imagingapparatus.

2. Description of the Related Art

In an imaging apparatus, such as a digital camera, or an optical device,such as a lens barrel, there is a high demand for a reduction in sizeand the improvement of the speed of auto-focusing is also required. Forthis reason, a focusing system is formed of a plurality of focus lensgroups to make a stroke length shorter than a stroke length that isobtained in a case in which a focusing system is formed of a singlefocus lens group (for example, JP2011-242791A (corresponding toUS2012/0262595A1)). Accordingly, the entire length of the lens barrelcan be reduced, and the speed of auto-focusing can be improved. Further,the performance degradation of a macro region can also be reduced in amacro lens.

Incidentally, there are many cases where an imaging apparatus, such as adigital camera, or an optical device, such as a lens barrel, is providedwith a vibration-proof mechanism. The vibration-proof mechanism includesa vibration-proof lens and actuators, and the actuators shift thevibration-proof lens in a pitch direction and a yaw direction.Accordingly, image blur caused by shake is suppressed (for example,JP2010-072062A (corresponding to US2010/0067889A1)). A linear actuator(voice coil motor), which includes a coil and magnets, is used as theactuator for shifting the vibration-proof lens.

Further, there is a case where a voice coil motor is used as an actuatorfor moving a movable lens, such as a focus lens group, other than arotary motor. Furthermore, such an optical device is provided withlight-amount control members, such as a stop, a neutral density (ND)filter, and a shutter, and actuators that drive these light-amountcontrol members.

In the optical device disclosed in JP2010-072062A, first and secondactuators shifting the vibration-proof lens in directions different fromeach other, a third actuator moving the movable lens and includingmagnets and a coil, and a fourth actuator operating the light-amountcontrol members and including magnets and a coil are received in a lensbarrel member, and these actuators are arranged not to overlap with eachother in a state in which these actuators are viewed in the direction ofan optical axis. Accordingly, magnetic interference between theactuators of the optical device is suppressed.

SUMMARY OF THE INVENTION

However, in a case in which all of the first to fourth actuators arearranged not to overlap with each other as in the optical devicedisclosed in JP2010-072062A in a state in which the first to fourthactuators are viewed in the direction of the optical axis, magneticinterference caused by the respective actuators can be suppressed but itis difficult to achieve efficient arrangement that can contribute to areduction in size.

In a case in which a focusing system is formed of a plurality of focuslens groups from the beginning to reduce the entire length of the lensbarrel and to improve the speed of auto-focusing, magnetic interferencebetween the voice coil motors of the vibration-proof mechanism and theposition sensors needs to be considered other than magnetic interferencebetween voice coil motors as actuators, which move the respective focuslens groups, and position sensors that detect the positions of therespective focus lens groups to be moved by these voice coil motors.Accordingly, in a case in which the respective actuators are arrangednot to overlap with each other in a state in which the respectiveactuators are viewed in the direction of the optical axis, magneticinterference cannot be efficiently suppressed and the respective partscannot be accurately operated.

An object of the invention is to provide an optical device and animaging apparatus that can much more mitigate magnetic interferencebetween actuators in a dual-focus type optical device individuallymoving first and second focus lenses.

An optical device according to an aspect of the invention includes afirst focus lens frame, a second focus lens frame, a blur-correctionlens frame, first to fourth voice coil motors, and first to fourthposition sensors. The first focus lens frame holds a first focus lensfor focusing a subject image and is moved in a direction of an opticalaxis of the first focus lens. The second focus lens frame is disposed soas to be spaced from the first focus lens in the direction of theoptical axis, holds a second focus lens for focusing the subject image,and is moved in the direction of the optical axis. The blur-correctionlens frame holds a blur-correction lens disposed between the first focuslens and the second focus lens and is moved in a direction orthogonal tothe optical axis of the first focus lens. The first voice coil motorincludes a first drive magnet, a first yoke, and a first coil mounted onthe first lens frame and moves the first lens frame in the direction ofthe optical axis in a case in which current flows in the first coil. Thesecond voice coil motor includes a second drive magnet, a second yoke,and a second coil mounted on the second lens frame and moves the secondlens frame in the direction of the optical axis in a case in whichcurrent flows in the second coil. The third voice coil motor includes athird drive magnet, a third yoke, and a third coil mounted on theblur-correction lens frame and moves the blur-correction lens frame in afirst direction in a plane orthogonal to the optical axis in a case inwhich current flows in the third coil. The fourth voice coil motorincludes a fourth drive magnet, a fourth yoke, and a fourth coil mountedon the blur-correction lens frame and moves the blur-correction lensframe in a second direction orthogonal to the first direction in a planeorthogonal to the optical axis in a case in which current flows in thefourth coil. The first position sensor magnetically detects a positionof the first lens frame in the direction of the optical axis. The secondposition sensor magnetically detects a position of the second lens framein the direction of the optical axis. The third position sensormagnetically detects a position of the blur-correction lens frame in thefirst direction. The fourth position sensor magnetically detects aposition of the blur-correction lens frame in the second direction. In astate in which the first position sensor, the second position sensor,the third voice coil motor, and the fourth voice coil motor are viewedin the direction of the optical axis, a line connecting the firstposition sensor to the optical axis is set as a first reference line anda line orthogonal to the first reference line and passing through theoptical axis is set as a second reference line. The first positionsensor and the second position sensor are arranged in a first region ofthe first region and a second region partitioned by the second referenceline. The third drive magnet and the third yoke of the third voice coilmotor and the fourth drive magnet and the fourth yoke of the fourthvoice coil motor are arranged in the second region.

It is preferable that the third position sensor and the fourth positionsensor are arranged so as to be symmetric with respect to the firstreference line. In this case, the deviation of the influence of themagnetism from the first and second voice coil motors on the third andfourth position sensors can be prevented, and vibration-proofperformance can be improved. It is preferable that the first positionsensor and the second position sensor are arranged so as to overlap witheach other in a state in which the first position sensor and the secondposition sensor are viewed in the direction of the optical axis. In thiscase, the influence of magnetism can be efficiently suppressed. Further,it is preferable that the third voice coil motor and the fourth voicecoil motor are arranged so as to be symmetric with respect to the firstreference line in a state in which the third voice coil motor and thefourth voice coil motor are viewed in the direction of the optical axis.Even in this case, since the first position sensor and the secondposition sensor are spaced so as to be equidistant from the third voicecoil motor and the fourth voice coil motor, the influence of themagnetism of the third voice coil motor and the fourth voice coil motorcan be suppressed so as to be more uniform.

It is preferable that each of the first position sensor and the secondposition sensor includes a first sensor magnet and a first magneticsensor magnetically detecting a change in a position of the first sensormagnet, each of the third position sensor and the fourth position sensorincludes a second sensor magnet and a second magnetic sensormagnetically detecting a change in a position of the second sensormagnet, the second magnetic sensor is a Hall element, and the firstmagnetic sensor is a magnetic sensor detecting magnetism weaker thanmagnetism to be detected by the Hall element. In this case, since thefirst and second position sensors, which include the first magneticsensors detecting magnetism weaker than magnetism to be detected by aHall element, can be spaced from the magnets and the yokes of the thirdand fourth voice coil motors on which the influence of magnetism isgreatest, the influence of the magnetism from the magnets and the yokesof the third and fourth voice coil motors can be efficiently suppressed.

It is preferable that the optical device further includes a pair offirst guide members guiding the first lens frame in the direction of theoptical axis and guide member-sliding portions which are formed on thefirst lens frame and on which the first guide members slide. The pair offirst guide members is disposed on the first reference line with theoptical axis interposed therebetween. The first coil is disposed on anouter periphery of the first focus lens. A plurality of the first drivemagnets and a plurality of the first yokes are provided, and theplurality of first drive magnets and the plurality of first yokes arearranged so as to be symmetric with respect to the first reference line.Further, the second coil is disposed on an outer periphery of the secondfocus lens. A plurality of the second drive magnets and a plurality ofthe second yokes are provided, and the plurality of second drive magnetsand the plurality of second yokes are arranged so as to be symmetricwith respect to the first reference line. In this case, since the pairof second guide members is disposed for one coil on the first referenceline with the optical axis interposed therebetween and the magnets andthe yokes are arranged so as to be symmetric with respect to the firstreference line, the coil, the magnets, and the yokes are arranged atsymmetric positions in balance. Accordingly, the first voice coil motorand the second voice coil motor can be smoothly operated.

It is preferable that the number of each of the first drive magnets, thefirst yokes, the second drive magnets, and the second yokes is four andthe respective magnets and the respective yokes are arranged so as to besymmetric with respect to the second reference line. Further, it ispreferable that the first coil and the second coil are formed in ahexagonal shape in a state in which the first coil and the second coilare viewed in the direction of the optical axis. Since theabove-mentioned arrangement is made, the respective members are arrangedin balance. Accordingly, the first voice coil motor and the second voicecoil motor can be more smoothly operated.

It is preferable that the first and second drive magnets of the firstand second voice coil motors have the same shape, the first and secondyokes of the first and second voice coil motors have the same shape, andthe first and second coils of the first and second voice coil motorshave the same shape. Further, it is preferable that a moving distance ofthe first focus lens in the direction of the optical axis is equal to amoving distance of the second focus lens in the direction of the opticalaxis. Furthermore, it is preferable that the moving distance of thefirst focus lens in the direction of the optical axis is equal to themoving distance of the second focus lens in the direction of the opticalaxis and a weight of the first focus lens is equal to a weight of thesecond focus lens. Since these are formed to have the same structure,not only the number of types of components is reduced but also the firstand second voice coil motors are easily synchronized with each other.

It is preferable that an imaging apparatus according to another aspectof the invention includes the optical device and an imaging elementtaking the subject image to be obtained through the optical device.Further, it is preferable that the optical device is included in anexchangeable lens unit including a connector that is attachable to anddetachable from a camera body including the imaging element in theimaging apparatus according to another aspect of the invention.

According to the aspects of the invention, it is possible to much moremitigate magnetic interference between voice coil motors and magneticsensors in a dual-focus type optical device individually moving firstand second focus lenses by voice coil motors.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view showing the schematic structure of animaging apparatus according to an embodiment of the invention.

FIG. 2 is an exploded perspective view showing a first focus mechanism,a stop mechanism, a vibration-proof mechanism, and a second focusmechanism that are disassembled in the direction of an optical axis.

FIG. 3 is a perspective view showing a state in which the first focusmechanism is disassembled in the direction of the optical axis and isviewed from the front side.

FIG. 4 is a perspective view showing a state in which the first focusmechanism is disassembled in the direction of the optical axis and isviewed from the rear side.

FIG. 5 is a front view of main portions of the first focus mechanism andthe vibration-proof mechanism that are viewed in the direction of theoptical axis.

FIG. 6 is a back view of a focus lens frame that is viewed in thedirection of the optical axis.

FIG. 7 is a perspective view showing main portions of the first focusmechanism, the vibration-proof mechanism, and the second focus mechanismthat are disassembled in the direction of the optical axis.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown in FIG. 1, an imaging apparatus 10 according to an embodimentof the invention includes a lens unit 11 as an optical device and acamera body 12. The lens unit 11 is formed as an exchangeable lens unit.The lens unit 11 includes a connector 13 that is attachable to anddetachable from the camera body 12. The lens unit 11 may be formedintegrally with the camera body 12.

The lens unit 11 comprises an optical system 14 in a lens barrel member19. The optical system 14 includes a first lens 21, a second lens 22, athird lens 23, a fourth lens 24, and a fifth lens 25 that are arrangedin this order from a subject side along an optical axis Ax. Each of thefirst to fifth lenses 21 to 25 is schematically shown as one lens, butmay be a plurality of lens groups.

The camera body 12 comprises an imaging element 7 that takes an opticalimage of a subject obtained through the optical system 14. A controller8 inputs information about various imaging conditions, such as animaging timing, to the imaging element 7, and receives image signalsthat are taken by and output from the imaging element 7. Then, thecontroller 8 performs analog processing and digital processing on thereceived image signals and generates taken image data to be output.

As also shown in FIG. 2, a first focus mechanism 15, a stop mechanism16, a vibration-proof mechanism 17, and a second focus mechanism 18 arearranged in the lens barrel member 19 in this order from the subjectside.

A focus ring 20 is rotatably mounted on the outer periphery of the lensbarrel member 19. In a case in which manual focusing is to be performed,for example, a first focus lens 22 as the second lens 22 and a secondfocus lens 24 as the fourth lens 24 are individually moved in thedirection of the optical axis Ax (hereinafter, the direction of theoptical axis) according to the rotation of the focus ring 20 when thefocus ring 20 is rotated. The first focus lens 22 and the second focuslens 24 are arranged at predetermined positions corresponding to animaging distance in the direction of the optical axis by the movement ofthe first focus lens 22 and the second focus lens 24, and can performfocusing.

The first lens 21 and the fifth lens 25 are stationary lenses, and arefixed on the front end side (subject side) and rear end side (imagingelement 7 side) of the lens barrel member 19, respectively. The firstfocus lens 22 as the second lens 22, a blur-correction lens 23 as thethird lens 23, and the second focus lens 24 as the fourth lens 24 aremovable lenses.

The first focus lens 22 is driven by the first focus mechanism 15 and ismoved in the direction of the optical axis. The second focus lens 24 isdriven by the second focus mechanism 18 and is moved in the direction ofthe optical axis.

As shown in FIGS. 3 and 4, the first focus mechanism 15 includes a focuslens frame 30 (corresponding to a first lens frame), a voice coil motor31 for focusing (hereinafter, referred to as a VCM, corresponding to afirst VCM), a pair of guide rods 32 a and 32 b as first guide members, aposition sensor 33 for focusing as a first position sensor, and a baseplate 29 in a cylindrical focus barrel 28. The focus lens frame 30 holdsthe first focus lens 22. The focus lens frame 30 is held by the pair ofguide rods 32 a and 32 b so as to be movable in the direction of theoptical axis. The guide rods 32 a and 32 b are arranged so as toprotrude from the base plate 29 in a direction parallel to the opticalaxis Ax. The pair of guide rods 32 a and 32 b is arranged so as to bespaced from the optical axis Ax as a center in a diameter direction ofthe base plate 29 orthogonal to the optical axis Ax.

The VCM 31 for focusing comprises one coil 34 (corresponding to a firstcoil), four drive magnets 35 (corresponding to a first drive magnet),and four yokes 36 (corresponding to a first yoke), and moves the focuslens frame 30 in the direction of the optical axis in a case in whichcurrent flows in the coil 34.

The coil 34 is an air-core coil that is formed by winding a copper wireor the like. The coil 34 is mounted on the focus lens frame 30 at aposition outside the first focus lens 22.

As shown in FIG. 5, the coil 34 is formed in a hexagonal shape in astate in which the coil 34 is viewed in the direction of the opticalaxis. The coil 34 is formed in a substantially hexagonal shape which isvertically long and of which a pair of opposite sides is formed of longsides 34 a longer than the other four sides and the other four sides areformed of short sides 34 b. Further, since apex angle portions where theshort sides 34 b are connected to each other are subjected to chamferingand connecting sides 34 c formed by the chamfering are also included inthe coil 34, the coil 34 is formed exactly in an octagonal shape. Theoctagonal shape, which is formed by the chamfering of the apex angleportions as described above, is also a substantially hexagonal shape andis included in a hexagonal shape in the invention.

As shown in FIG. 6, the outer shape of the focus lens frame 30 is alsoformed of a substantially hexagonal shape as in the case of the coil 34in a state in which the focus lens frame 30 is viewed in the directionof the optical axis. Further, sliding portions 40 and 41 (correspondingto guide member-sliding portions) are formed in the middle portions ofthe pair of long sides 30 a in a circumferential direction so as toprotrude in the diameter direction passing through the optical axis Ax.A sliding cylinder 40 a is formed at the distal end of one slidingportion 40, and a sliding groove 41 a is formed at the distal end of theother sliding portion 41.

As shown in FIG. 3, the sliding cylinder 40 a is formed parallel withthe direction of the optical axis. One guide rod 32 a is inserted intothe sliding cylinder 40 a. Further, the guide rod 32 b is engaged withthe sliding groove 41 a. Since the pair of guide rods 32 a and 32 b isengaged with the sliding cylinder 40 a and the sliding groove 41 a, thefocus lens frame 30 is moved and guided in the direction of the opticalaxis.

As shown in FIGS. 3 and 4, each yoke 36 is formed of a magnetic body andis formed in a U shape where an outer yoke 36 a and an inner yoke 36 bface each other so as to clamp the coil 34 and each drive magnet 35. Thedrive magnet 35 is mounted on the inner surface of each outer yoke 36 a.

Openings 30 e (see FIG. 6) into which the inner yokes 36 b are to beinserted are formed at the focus lens frame 30. After the inner yokes 36b are inserted into the openings 30 e, connecting plates 36 d are fittedto notches of the outer and inner yokes 36 a and 36 b. Accordingly, thedrive magnet 35 and the yoke 36 are arranged at each of the four shortsides 34 b of the coil 34 as shown in FIG. 5.

The yokes 36 are fixed to the inner peripheral surface of the focusbarrel 28. The coil 34 is disposed between the yokes 36 and the drivemagnets 35, and is moved in the direction of the optical axis in amagnetic field that is generated by the drive magnets 35 in a case inwhich current flows in the coil 34.

The position sensor 33 for focusing detects the position of the focuslens frame 30 in the direction of the optical axis. The position sensor33 for focusing includes a rod-like position-detection magnet 33 a(corresponding to a first sensor magnet) and a magnetic sensor 33 b(corresponding to a first magnetic sensor). The position-detectionmagnet 33 a is embedded in the outer surface of the sliding cylinder 40a of the focus lens frame 30, and the surface of the position-detectionmagnet 33 a is exposed to the outside.

A GMR element using a giant magneto resistive effect (GMR) is used asthe magnetic sensor 33 b. The magnetic sensor 33 b is mounted on theoutside of the focus barrel 28. An opening 28 a (see FIGS. 3 and 4),which allows the position-detection magnet 33 a to be exposed to theoutside of the focus barrel 28, is formed at the focus barrel 28. Themagnetic sensor 33 b is disposed close to the position-detection magnet33 a through the opening 28 a. Accordingly, the magnetic sensor 33 bdetects the magnetism of the position-detection magnet 33 a and outputsa detection signal corresponding to the strength of the magnetism.

An output signal of the magnetic sensor 33 b is sent to the controller 8of the camera body 12. The controller 8 detects the position of thefocus lens frame 30 in the direction of the optical axis on the basis ofthe output signal of the magnetic sensor 33 b, and moves the first focuslens 22 to a desired position by the first focus mechanism 15 to performfocusing.

In this embodiment, as shown in FIG. 5, guide positions where the focuslens frame 30 is to be guided by the guide rods 32 a and 32 b, and thepositions where a magnetic force is to be applied to the focus lensframe 30 in a case in which current flows in the coil 34 are positionedon concentric circles having a center on the optical axis Ax. For thisreason, the guide rods 32 a and 32 b, the drive magnets 35, and theyokes 36 are arranged around the optical axis Ax in balance.Accordingly, the focus lens frame 30 can be smoothly moved in thedirection of the optical axis in a case in which current flows in thecoil 34.

As shown in FIG. 2, the second focus mechanism 18 comprises a focus lensframe 30 (corresponding to a second lens frame), a VCM 31 for focusing(corresponding to a second VCM), a pair of guide rods 32 a and 32 b(second guide members), and a position sensor 33 for focusing (a secondposition sensor for focusing) in a cylindrical focus barrel 28 (see FIG.1). The second focus mechanism 18 has the same structure as the firstfocus mechanism 15 except that the second focus lens 24 is mounted onthe focus lens frame 30 instead of the first focus lens 22. For thisreason, the same components are denoted by the same reference numeralsand the repeated description thereof will be omitted.

In a case in which the respective components need to be identifiedbetween the first focus mechanism 15 and the second focus mechanism 18,“first” is added to the components of the first focus mechanism 15 and“second” is added to the components of the second focus mechanism 18. Adirection in which the second focus mechanism 18 is mounted and adirection in which the first focus mechanism 15 is mounted are oppositeto each other in a front-rear direction, but may be the same direction.As shown in FIG. 7, the first focus mechanism 15 and the second focusmechanism 18 are arranged so that the first position sensor 33 forfocusing and the second position sensor 33 for focusing (correspondingto a second position sensor) overlap with each other in a state in whichthe first position sensor 33 for focusing and the second position sensor33 for focusing are viewed in the direction of the optical axis.

As shown in FIG. 2, the stop mechanism 16 and the vibration-proofmechanism 17 are mounted between the first focus mechanism 15 and thesecond focus mechanism 18. The stop mechanism 16 includes a stop leafblade 16 a that is disposed around the optical axis Ax. The amount ofimaging light, which is to be incident on the camera body 12, isadjusted by an increase and reduction in the diameter of a stop openingthat is formed by the stop leaf blade 16 a.

The vibration-proof mechanism 17 includes a blur-correction lens 23, ablur-correction lens frame 51, an X-direction VCM 52 (corresponding to athird VCM), a Y-direction VCM 53 (corresponding to a fourth VCM), anX-direction position sensor 54 (corresponding to a third positionsensor, see FIG. 7), a Y-direction position sensor 55 (corresponding toa fourth position sensor, see FIG. 7), and a fixed plate 56 (see FIG.5). The blur-correction lens frame 51 holds the blur-correction lens 23,and is mounted on the fixed plate 56 so as to be movable in an Xdirection (corresponding to a first direction, see FIG. 7) and a Ydirection (corresponding to a second direction, see FIG. 7).

The X-direction VCM 52 includes drive magnets 52 a (corresponding to athird drive magnet), a coil 52 b (corresponding to a third coil), andyokes 52 c (corresponding to a third yoke), and moves theblur-correction lens frame 51 in the X direction. The drive magnets 52 aare fixed to the yokes 52 c, and the yokes 52 c are fixed to the fixedplate 56. The coil 52 b is fixed to the blur-correction lens frame 51.The Y-direction VCM 53 includes drive magnets 53 a (corresponding to afourth drive magnet), a coil 53 b (corresponding to a fourth coil), andyokes 53 c (corresponding to a fourth yoke), and moves theblur-correction lens frame 51 in the Y direction. The drive magnets 53 aare fixed to the yokes 53 c, and the yokes 53 c are fixed to the fixedplate 56. Further, the coil 53 b is fixed to the blur-correction lensframe 51.

The X-direction position sensor 54 detects the position of the lens ofthe blur-correction lens frame 51 in the X direction, and theY-direction position sensor 55 detects the position of the lens of theblur-correction lens frame 51 in the Y direction. The X-directionposition sensor 54 includes a position-detection magnet 54 a(corresponding to a second sensor magnet) and a magnetic sensor 54 b(corresponding to a second magnetic sensor). Likewise, the Y-directionposition sensor 55 also includes a position-detection magnet 55 a(corresponding to a second sensor magnet) and a magnetic sensor 55 b(corresponding to a second magnetic sensor).

A Hall element is used as each of the magnetic sensors 54 b and 55 b.The magnetic sensors 54 b and 55 b are fixed to, for example, the fixedplate 56. Further, the position-detection magnets 54 a and 55 a arefixed to the blur-correction lens frame 51. The magnetic sensors 54 band 55 b are arranged close to the position-detection magnets 54 a and55 a, respectively. Accordingly, the magnetic sensors 54 b and 55 bdetect the magnetism of the position-detection magnets 54 a and 55 a,and outputs detection signals corresponding to the strength of themagnetism. The detection signals are sent to the controller 8. In a casein which the movement of the imaging apparatus 10 is detected by avibration gyro sensor (not shown), the controller 8 corrects image blurby displacing the blur-correction lens 23 in an XY plane using theX-direction VCM 52 and the Y-direction VCM 53 in a direction where imageblur caused by this movement is to be canceled.

Next, the action of this embodiment will be described. In a case inwhich imaging is started by a release operation, the first and secondfocus mechanisms 15 and 18 are operated and the first and second focuslenses 22 and 24 are moved in the direction of the optical axis, andfocusing control is performed. In a case in which the focusing controlof a plurality of focus lenses 22 and 24 is performed by the first andsecond focus mechanisms 15 and 18 as described above, a lens-movingdistance is dispersed. Accordingly, quick focusing can be performed.Particularly, since the plurality of focus lenses 22 and 24 are moved,quick and accurate focusing can be performed in macro imaging. Further,in a case in which the shake of the imaging apparatus 10 is detected,the vibration-proof mechanism 17 is operated and moves theblur-correction lens 23 in the XY plane. Accordingly, image blur iscorrected.

As shown in FIGS. 1 and 2, the first focus mechanism 15, the stopmechanism 16, the vibration-proof mechanism 17, and the second focusmechanism 18 are arranged in this order in the lens barrel member 19 soas to be close to each other. For this reason, there is a concern thatmagnetic interference may occur in a case in which the VCMs 31, 52, and53 as drive sources of the first focus mechanism 15, the vibration-proofmechanism 17, and the second focus mechanism 18 and the position sensors33, 54, and 55 formed of magnetic sensors are not arranged atappropriate positions. Since the position sensors 33, 54, and 55 cannotaccurately detect positions in a case in which magnetic interferenceoccurs, malfunction occurs or abnormal noises are generated.

Particularly, since each of the first and second focus mechanisms 15 and18 detects the position of the focus lens frame 30 by the positionsensor 33 for focusing that uses a GMR element as the magnetic sensor 33b, each of the first and second focus mechanisms 15 and 18 is likely tobe affected by magnetic fields generated from the VCMs 52 and 53 of theadjacent vibration-proof mechanism 17 and the position sensors 54 and 55that use Hall elements as the magnetic sensors 54 b and 55 b. For thisreason, in a state in which the position sensor 33 for focusing isviewed in the direction of the optical axis, the position sensor 33 forfocusing, which uses a GMR element, is disposed at a position farthestfrom the VCMs 52 and 53 of the vibration-proof mechanism 17 and theposition sensors 54 and 55 to suppress the occurrence of magneticinterference.

The arrangement of the respective position sensors 33, 54, and 55 andthe respective VCMs 31, 52, and 53 will be described below using a firstreference line BL1 and a second reference line BL2 with reference toFIG. 5. The first reference line BL1 is the extension line of a lineconnecting the position sensor 33 for focusing to the optical axis Ax ina state in which the position sensor 33 for focusing is viewed in thedirection of the optical axis. The second reference line BL2 is a linethat passes through the optical axis Ax and is orthogonal to the firstreference line BL1. Two lines, which cross the first reference line BL1and the second reference line BL2 at an angle of 45°, are a horizontalline HL parallel to the X direction and a vertical line VL parallel tothe Y direction.

The focus lens frame 30 is held by the guide rods 32 a and 32 b as apair of guide members 32 so as to be movable in the direction of theoptical axis. The guide rods 32 a and 32 b are arranged on the firstreference line BL1 with the optical axis Ax interposed therebetween. Thecoil 34 is disposed on the outer periphery of the first focus lens 22,and includes the pair of opposite long sides 34 a and two pairs of shortsides 34 b connecting the long sides 34 a and is formed in asubstantially hexagonal shape. Four drive magnets 35 and four yokes 36are arranged on the short sides 34 b of the coil 34, respectively. Thefour drive magnets 35 and the four yokes 36 are arranged so as to besymmetric with respect to the first reference line BL1 and the secondreference line BL2.

The position sensor 33 for focusing is disposed in a first region AR1 ofthe first region AR1 and a second region AR2 that are partitioned by thesecond reference line BL2. In contrast, the third drive magnets 52 a,the third coil 52 b, and the third yokes 52 c of the X-direction VCM(third VCM) 52 of the vibration-proof mechanism 17 and the fourth drivemagnets 53 a, the fourth coil 53 b, and the third yokes 52 c of theY-direction VCM (fourth VCM) 53 are arranged in the second region AR2 atpositions that are symmetric with respect to the first reference lineBL1. As described above, the respective magnets 52 a and 53 a and therespective coils 52 b and 53 b of the respective VCMs 52 and 53 of thevibration-proof mechanism 17 are spaced so as to be equidistant from theposition sensor 33 for focusing in a state in which the respectivemagnets 52 a and 53 a and the respective coils 52 b and 53 b of therespective VCMs 52 and 53 of the vibration-proof mechanism 17 are viewedin the direction of the optical axis. Accordingly, the influence ofmagnetism, which is given to the position sensor 33 for focusing by theX-direction VCM 52 and the Y-direction VCM 53, can be suppressed in thefirst and second focus mechanisms 15 and 18. Accordingly, focusing canbe accurately performed without the deterioration of the positiondetection accuracy of the position sensor 33 for focusing. Further,since there is no unstable operation based on the deterioration of theaccuracy of the position detected by the position sensor 33 forfocusing, the generation of abnormal noises and the like are suppressed.

Since the first position sensor 33 for focusing of the first focusmechanism 15 and the second position sensor 33 for focusing of thesecond focus mechanism 18 are arranged so as to overlap with each otheras shown in FIG. 7 in a state in which the first position sensor 33 forfocusing and the second position sensor 33 for focusing are viewed inthe direction of the optical axis, the deviation of magnetism around theoptical axis Ax, which is caused by each position sensor 33 forfocusing, can be prevented. Further, since the drive magnets 52 a and 53a and the coils 52 b and 53 b of the X-direction VCM 52 and theY-direction VCM 53 are arranged at positions symmetric with respect tothe first reference line BL1 in a state in which the drive magnets 52 aand 53 a and the coils 52 b and 53 b are viewed in the direction of theoptical axis, the position sensor 33 for focusing is spaced so as to beequidistant from the X-direction VCM 52 and the Y-direction VCM 53. Forthis reason, the influence of the magnetism of the X-direction VCM 52and the Y-direction VCM 53 can be suppressed so as to be more uniform.

A GMR element, which can detect magnetism weaker than magnetism to bedetected by a Hall element, is used in the position sensor 33 forfocusing. For this reason, the position sensor 33 for focusing candetect a focus position with high accuracy. On the other hand, theposition sensor 33 for focusing is likely to be affected by themagnetism of other magnets. For this reason, the position sensor 33 forfocusing is spaced from the magnets 52 a and 53 a and the coils 52 b and53 b of the X-direction VCM 52 and the Y-direction VCM 53, so that theinfluence of the magnetism of the magnets 52 a and 53 a and the coils 52b and 53 b on the position sensor 33 for focusing can be efficientlysuppressed.

Further, since the position sensors 54 and 55 are arranged so as to besymmetric with respect to the first reference line BL1, the deviation ofthe influence of the magnetism from the first and second VCMs 31 forfocusing on the position-detection magnets 54 a and 55 a can beprevented. Accordingly, vibration-proof performance can be improved.

Since the pair of guide members 32 is disposed for one coil 34 on thefirst reference line BL1 with the optical axis Ax interposedtherebetween and the drive magnets 35 and the yokes 36 are arranged soas to be symmetric with respect to the first reference line BL1, therespective members, such as the coil 34, the drive magnets 35, and theyokes 36, are arranged at symmetric positions in balance. Accordingly,the VCM 31 for focusing can be smoothly operated.

Since the number of each of the drive magnets 35 (corresponding to thefirst and second drive magnets) and the yokes 36 (corresponding to thefirst and second yokes) of each of the first and second focus mechanisms15 and 18 is four and the respective drive magnets 35 and the respectiveyokes 36 are arranged so as to be symmetric with respect to the secondreference line BL2, the respective members are arranged in balance. Forthis reason, the first and second focus mechanisms 15 and 18 can be moresmoothly operated. Further, since the coils 34 (corresponding to thefirst and second coils) of the first and second focus mechanisms 15 and18 are formed in a hexagonal shape in a state in which the coils 34 ofthe first and second focus mechanisms 15 and 18 are viewed in thedirection of the optical axis, the sliding portions 40 and 41 can bearranged on the pair of opposite sides and the magnets 35 and the yokes36 can be arranged on the other two pairs of sides. Accordingly, sincebalanced arrangement can be made, the focus lens frame 30 can besmoothly moved.

Since the coils 34, the drive magnets 35, and the yokes 36 have the samestructure in the first and second focus mechanisms 15 and 18, not onlythe number of types of components is reduced but also the first andsecond focus mechanisms 15 and 18 are easily synchronized with eachother. In a case in which the moving distance of the first focus lens 22in the direction of the optical axis and the moving distance of thesecond focus lens 24 in the direction of the optical axis are set to beequal to each other, the first and second focus mechanisms 15 and 18 aremore easily synchronized with each other. Moreover, in a case in whichthe moving distance of the first focus lens 22 in the direction of theoptical axis and the moving distance of the second focus lens 24 in thedirection of the optical axis are set to be equal to each other and theweight of the first focus lens 22 and the weight of the second focuslens 24 are set to be equal to each other, the first and second focusmechanisms 15 and 18 are much more easily synchronized with each other.

Focus control and blur-correction are performed by the controller 8 ofthe camera body 12 in the embodiment. However, instead of this, acontroller may be provided in the lens unit 11, and focus control andblur-correction may be performed by the controller of the lens unit 11.

In a case in which a zoom mechanism is provided, a rotatable zoom ring(not shown) is provided and one or more lenses of the first lens 21 andlens groups of the respective mechanisms, such as the first focusmechanism 15, the stop mechanism 16, the vibration-proof mechanism 17,and the second focus mechanism 18, are moved in the direction of theoptical axis by an operation for rotating the zoom ring. Accordingly, azoom operation can be performed according to an operation for rotatingthe zoom ring.

EXPLANATION OF REFERENCES

7: imaging element

8: controller

10: imaging apparatus

11: lens unit

12: camera body

13: connector

14: optical system

15: first focus mechanism

16: stop mechanism

16 a: stop leaf blade

17: vibration-proof mechanism

18: second focus mechanism

19: lens barrel member

20: focus ring

21: first lens

22: first focus lens (second lens)

23: blur-correction lens (third lens)

24: second focus lens (fourth lens)

25: fifth lens

28: focus barrel

29: base plate

30: focus lens frame (first and second lens frames)

30 a: long side

30 e: opening

31: VCM for focusing (first and second voice coil motors)

32: guide member (first and second guide members)

32 a, 32 b: guide rod

33: position sensor for focusing (first and second position sensors)

33 a: position-detection magnet (first sensor magnet)

33 b: magnetic sensor (first magnetic sensor)

34: coil (first and second coils)

34 a: long side

34 b: short side

34 c: connecting side

35: drive magnet (first and second drive magnets)

36: yoke (first and second yokes)

36 a: outer yoke

36 b: inner yoke

36 d: connecting plate

40: sliding portion (guide member-sliding portion)

40 a: sliding cylinder

41: sliding portion (guide member-sliding portion)

41 a: sliding groove

51: blur-correction lens frame

52: X-direction VCM (third VCM)

52 a: drive magnet (third drive magnet)

52 b: coil (third coil)

52 c: yoke (third yoke)

53: Y-direction VCM (fourth VCM)

53 a: drive magnet (fourth drive magnet)

53 b: coil (fourth coil)

53 c: yoke (fourth yoke)

54: X-direction position sensor (third position sensor)

54 a: position-detection magnet (second sensor magnet)

54 b: magnetic sensor (second magnetic sensor)

55: Y-direction position sensor (fourth position sensor)

55 a: position-detection magnet (second sensor magnet)

55 b: magnetic sensor (second magnetic sensor)

56: fixed plate

Ax: optical axis

BL1: first reference line

BL2: second reference line

HL: horizontal line

VL: vertical line

AR1: first region

AR2: second region

What is claimed is:
 1. An optical device comprising: a first lens framethat holds a first focus lens for focusing a subject image and is movedin a direction of an optical axis of the first focus lens; a second lensframe that is disposed so as to be spaced from the first focus lens inthe direction of the optical axis, holds a second focus lens forfocusing the subject image, and is moved in the direction of the opticalaxis; a blur-correction lens frame that holds a blur-correction lensdisposed between the first focus lens and the second focus lens and ismoved in a direction orthogonal to the optical axis of the first focuslens; a first voice coil motor that includes a first drive magnet, afirst yoke, and a first coil mounted on the first lens frame and movesthe first lens frame in the direction of the optical axis in a case inwhich current flows in the first coil; a second voice coil motor thatincludes a second drive magnet, a second yoke, and a second coil mountedon the second lens frame and moves the second lens frame in thedirection of the optical axis in a case in which current flows in thesecond coil; a third voice coil motor that includes a third drivemagnet, a third yoke, and a third coil mounted on the blur-correctionlens frame and moves the blur-correction lens frame in a first directionin a plane orthogonal to the optical axis in a case in which currentflows in the third coil; a fourth voice coil motor that includes afourth drive magnet, a fourth yoke, and a fourth coil mounted on theblur-correction lens frame and moves the blur-correction lens frame in asecond direction orthogonal to the first direction in a plane orthogonalto the optical axis in a case in which current flows in the fourth coil;a first position sensor that magnetically detects a position of thefirst lens frame in the direction of the optical axis; a second positionsensor that magnetically detects a position of the second lens frame inthe direction of the optical axis; a third position sensor thatmagnetically detects a position of the blur-correction lens frame in thefirst direction; and a fourth position sensor that magnetically detectsa position of the blur-correction lens frame in the second direction,wherein in a case in which a line connecting the first position sensorto the optical axis is set as a first reference line and a lineorthogonal to the first reference line and passing through the opticalaxis is set as a second reference line in a state in which the firstposition sensor, the second position sensor, the third voice coil motor,and the fourth voice coil motor are viewed in the direction of theoptical axis, the first position sensor and the second position sensorare arranged in a first region of the first region and a second regionpartitioned by the second reference line and the third drive magnet andthe third yoke of the third voice coil motor and the fourth drive magnetand the fourth yoke of the fourth voice coil motor are arranged in thesecond region.
 2. The optical device according to claim 1, wherein thethird position sensor and the fourth position sensor are arranged so asto be symmetric with respect to the first reference line.
 3. The opticaldevice according to claim 1, wherein the first position sensor and thesecond position sensor are arranged so as to overlap with each other ina state in which the first position sensor and the second positionsensor are viewed in the direction of the optical axis.
 4. The opticaldevice according to claim 1, wherein the third voice coil motor and thefourth voice coil motor are arranged so as to be symmetric with respectto the first reference line in a state in which the third voice coilmotor and the fourth voice coil motor are viewed in the direction of theoptical axis.
 5. The optical device according to claim 1, wherein eachof the first position sensor and the second position sensor includes afirst sensor magnet and a first magnetic sensor that magneticallydetects a change in a position of the first sensor magnet, each of thethird position sensor and the fourth position sensor includes a secondsensor magnet and a second magnetic sensor that magnetically detects achange in a position of the second sensor magnet, and the secondmagnetic sensor is a Hall element, and the first magnetic sensor is amagnetic sensor that detects magnetism weaker than magnetism to bedetected by the Hall element.
 6. The optical device according to claim5, further comprising: a pair of first guide members that is disposed onthe first reference line with the optical axis interposed therebetweenand guides the first lens frame in the direction of the optical axis;and guide member-sliding portions which are formed on the first lensframe and on which the first guide members slide, wherein the first coilis disposed on an outer periphery of the first focus lens, and aplurality of the first drive magnets and a plurality of the first yokesare provided, and the plurality of first drive magnets and the pluralityof first yokes are arranged so as to be symmetric with respect to thefirst reference line.
 7. The optical device according to claim 5,further comprising: a pair of second guide members that is disposed onthe first reference line with the optical axis interposed therebetweenand guides the second lens frame in the direction of the optical axis;and guide member-sliding portions which are formed on the second lensframe and on which the second guide members slide, wherein the secondcoil is disposed on an outer periphery of the second focus lens, and aplurality of the second drive magnets and a plurality of the secondyokes are provided, and the plurality of second drive magnets and theplurality of second yokes are arranged so as to be symmetric withrespect to the first reference line.
 8. The optical device according toclaim 7, wherein a number of each of the first drive magnets, the firstyokes, the second drive magnets, and the second yokes is four, and therespective magnets and the respective yokes are arranged so as to besymmetric with respect to the second reference line.
 9. The opticaldevice according to claim 8, wherein the first coil and the second coilare formed in a hexagonal shape in a state in which the first coil andthe second coil are viewed in the direction of the optical axis.
 10. Theoptical device according to claim 9, wherein the first and second drivemagnets of the first and second voice coil motors have a same shape, thefirst and second yokes of the first and second voice coil motors have asame shape, and the first and second coils of the first and second voicecoil motors have a same shape.
 11. The optical device according to claim10, wherein a moving distance of the first focus lens in the directionof the optical axis is equal to a moving distance of the second focuslens in the direction of the optical axis.
 12. The optical deviceaccording to claim 10, wherein the moving distance of the first focuslens in the direction of the optical axis is equal to the movingdistance of the second focus lens in the direction of the optical axis,and a weight of the first focus lens is equal to a weight of the secondfocus lens.
 13. An imaging apparatus comprising: the optical deviceaccording to claim 1; and an imaging element that takes the subjectimage to be obtained through the optical device.
 14. The imagingapparatus according to claim 13, wherein the optical device is includedin an exchangeable lens unit including a connector that is attachable toand detachable from a camera body including the imaging element.